The research project is designed to test the hypothesis that there is a direct correlation between dietary iron intake and risk of cancer. On this basis, high iron intake would be associated with an increased risk of cancer compared to low intake. There are at least two possible biological mechanisms that provide a rationale for the hypothesis: 1) iron can catalyze the production of oxygen radicals which may be proximate carcinogens, and 2) iron may be a limiting nutrient to the growth and development of a transformed cell in the human body. There is evidence that increased body iron stores are associated with an increased risk of cancer. However, since each person is an individual biochemically, iron stores may, or may not be influenced by dietary iron intake within the normal ranges of consumption. The best, and perhaps only way of testing the hypothesis effectively is by use of a large population sample followed prospectively since dietary habits well before onset of disease must be evaluated. The NHANES I population cohort offers the opportunity to examine the relation of dietary iron intake and certain biochemical markers of iron stores with subsequent long term risk of cancer. In addition, the interaction of the "oxidant" iron with "anti-oxidants" (such as vitamines C and E) might be amenable to analysis. The implications of a positive reult in the proposed study might be at odds with the conventional wisdom concernign iron that holds: since iron-deficiency anemia is a serious health problem world-wide, iron repletion should be a primary dietary goal. It may become apparent through this and other studies that body iron stores are important up to a certain level but that above this level the benefits are counter-balanced by increased risk of cancer (or infectious disease).